1. Field of the Invention
The present invention relates to server virtualization technologies for allowing a single physical server to operate as one or more independent virtual servers. This invention also relates to a technique for dynamically modifying the configuration of a cluster system which is arranged by virtual servers to thereby reduce electrical power consumption.
2. Description of the Related Art
In recent years, aggressive attempts are made to promote the introduction of virtualization technology into business-entity information systems (referred to hereinafter as corporate systems), which are information systems for use in business enterprises or companies. By the virtualization technology, physical or “real” servers that constitute a corporate system are replaced by virtual servers, resulting in a decrease in physical server number owing to server integration (i.e., server consolidation). By such reduction of the physical server number, companies may obtain the merit of reduction of physical server introduction costs and power consumption.
In corporate systems, the workload can vary depending upon operation time periods and timings. In a corporate system which provides services by a cluster system that is constituted from a plurality of virtual servers, when all the virtual servers are rendered operative in a way tuned with a peak of the workload, redundant computing resources (e.g., central processing unit (CPU), memory or the like) relative to the workload consume surplus electrical power being supplied thereto, resulting in incurrence of much waste. Known approaches to reducing such surplus power include load change-sensitive dynamic system configuration alteration and workload consolidation techniques, some of which are disclosed in US Published Patent Application 2005/0060590A1 and in the article by Dara Kusic et al., entitled “Power and performance management of virtualized computing environments via lookahead control”, Cluster Computing, Kluwer Academic Publishers (March 2009).
It should be noted that the cluster system as used herein is a system which is arranged to contain a plurality of virtual servers that perform the same computation processing and which has a function module (e.g., workload dispersion device, also known as load balancer) operative to dispatch and allocate requests from clients with respect to the plurality of virtual servers. The computation processing is executed by an application server, which may be a software program running on a virtual server(s).
The US 2005/0060590A1 cited above discloses therein a system which includes a plurality of physical servers each having a plurality of virtual servers operating thereon. In the subject system, a physical server with operative virtual servers is modified in a way pursuant to the workload in order to reduce power consumption (this is called the relocation or “migration” of virtual servers). More specifically, a computing resource amount required is derived through computation from a present workload state as a necessary virtual server number; then, a virtual server or servers are migrated to the minimum required physical server(s) for enabling operations of the derived number of virtual servers (this processing is herein denoted as “workload consolidation”). As a result of this, a surplus physical server with no operative virtual servers is generated. The power supply of such physical server is turned off, thereby reducing power consumption.
In the Dara Kusic et al. cited above, a system environment is disclosed, wherein a plurality of cluster systems each being configured from virtual servers are rendered operative on a plurality of physical servers. In this environment, the cluster systems are applied scale-in/scale-out processing in accordance with the workload in order to reduce power consumption.
The scale-in is a processing operation for halting the request allocation with respect to one or more than one virtual server constituting a cluster system and for deleting the virtual server from the cluster system. By this scale-in, the computing resource amount that is consumed by the cluster system is reduced. Furthermore, a physical server with the number of the in-operation virtual servers becoming zero (0) due to deactivation of the scale-in-executed virtual server is powered off, thereby reducing power consumption.
On the other hand, the scale-out is a processing operation for adding one or more virtual servers to a cluster system and for starting the request allocation to the added virtual server. The scale-out results in an increase in computing resource amount to be consumed by the cluster system. Additionally, prior to execution of the scale-out, virtual server start-up processing is performed when the need arises.
In the Dara Kusic et al., a specific level of consumed power appropriate for the number of operative virtual servers of each physical server is obtained in advance as power consumption data. Using this pre-obtained power consumption data, processing is performed for deleting from the cluster system a virtual server which is expected to offer the highest power consumption reduction effect owing to the deactivation in the scale-in event. The virtual server that was deleted from the cluster system is rendered inoperative. In the scale-out event, processing is performed for adding to the cluster system a virtual server which is lowest in rise-up of power consumption when it is activated. Prior to this adding processing, the virtual server is activated as needed.